Oil changes should be at about 5-6k kms. 7-8k kms if you doing highway stuff.
Provided you arent running lean or getting predetonation your engine should last till around 250-300 k kms or more.
If the timing belt snaps its goneski, same with if an idler bearing etc seizes. Unforseen things can happen but unlikely. Helps if you can service your own car or know a good mechanic.
Good idea to throw it on the dyno for a power run (about $50) and check the 02 sensor is taking care of the closed loop (AFR 14.7)
Dont worry so much. Mine has 120k on it and not a sign of probs.
My old corolla which I revved over 7k each day was sitting on 230k kms without any trouble at all